Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1999-11-16
2001-07-10
Moore, Margaret G. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S860000, C528S014000
Reexamination Certificate
active
06258891
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a solventless process for anionically polymerizing polysiloxane polymers. More particularly, this invention relates to an improved process for making polyethylene-polysiloxane or polystyrene-polysiloxane block copolymers.
BACKGROUND OF THE INVENTION
U.S. Pat. No. 5,618,903 describes polyethylene-polysiloxane block copolymers for use in release surface compositions. Such polymers and polysiloxane homopolymers and other copolymers are made by a process which utilizes a volatile hydrocarbon liquid as the solvent for anionic polymerization. This process necessarily requires an expensive solvent removal step and equipment for recycle of the solvent. Thus, it can be seen that it would be advantageous to provide a process to make block copolymers of this type which does not require the use of a volatile hydrocarbon solvent.
SUMMARY OF THE INVENTION
This invention is a solventless process for anionically polymerizing polysiloxane polymers. No volatile hydrocarbon solvent is used. A cyclic siloxane monomer and any comonomer are introduced into a molten polymer phase of a low molecular weight polymer that has a melting point within the polymerization temperature range for the cyclic siloxanes and the comonomer, for example, 30 to 80° C. which is the melting point range for polyethylene wax which is preferred. A non-volatile hydrocarbon oil with a melting point in this range may also be used, especially if a final polymer containing oil is desired. The cyclic siloxane monomer is anionically polymerized in the molten polymer phase or the oil at 30 to 150° C. Ethylene and styrene are preferred comonomers. Neither the low molecular weight polymer nor the non-volatile oil are separated from the polysiloxane after termination of the polymerization.
A preferred embodiment is a process of polymerizing polyethylene-polysiloxane block copolymers which comprises:
(a) introducing ethylene monomer into a molten polyethylene wax having a melting point in the range of 30 to 80° C.,
(b) anionically polymerizing the ethylene at a temperature of 30 to 80° C. to form a living polyethylene block,
(c) introducing a cyclic siloxane monomer into the molten polyethylene wax,
(d) anionically polymerizing the siloxane monomer at a temperature of 30 to 150° C. on the living end of the polyethylene block, and
(e) terminating the polymerization.
The cyclic siloxane monomer which forms the polymerized polysiloxane block can be a cyclic siloxane monomer of the formula (R
1
R
2
SiO)
n
, where n can be 3 to 10, R
1
and R
2
are alkyl (C
1
-C
20
), alkenyl (C
2
-C
20
), hydrogen, benzyl or phenyl (including alkyl substituted aromatics and polycyclics) and R
1
and R
2
can be the same or different. The cyclic siloxane monomer is preferably hexamethylcyclotrisiloxane.
DETAILED DESCRIPTION OF THE INVENTION
In general, when solution anionic techniques are used, polymers of anionically polymerizable monomers are prepared by contacting the monomer to be polymerized simultaneously or sequentially with an anionic polymerization initiator such as Group IA metals, their alkyls, amides, silanolates, naphthalides, biphenyls and anthracenyl derivatives. It is preferable to use an organo alkali metal (such as sodium or potassium) compound in the molten polymer phase or the non-volatile oil at a temperature within the polymerization range for the cyclic siloxanes and the comonomers, preferably at a temperature within the range from 30° C. to 150° C. Particularly effective anionic polymerization initiators are organo lithium compounds having the general formula:
RLi
n
wherein R is an aliphatic, cycloaliphatic, aromatic or alkyl-substituted aromatic hydrocarbon radical having from 1 to 20 carbon atoms; and n is an integer of 1-4.
Since these polysiloxane polymers are intended to be used as additives or modifiers, the solventless polymerization medium does not have to be removed. Actually, this solventless process can be carried out in any hydrocarbon polymer system which exists as a melt phase within the 30 to 80° C. temperature range, e.g., low molecular polyethylene wax, which is preferred, low molecular weight polypropylene, polybutylene, polystyrene, polyisobutylene, hydrogenated polybutadiene or polysioprene, etc. Non-volatile processing oils such as SHELLFLEX® oil can also be used as the polymerization medium.
Polysiloxane homopolymers, such as polydimethylsiloxane or polydiphenylsiloxane can be made according to this process. Block copolymers containing polysiloxane blocks and blocks of other anionically polymerizable monomers can also be made this way. Random copolymer blocks can also be included in the block copolymers. Ethylene and styrene are the preferred comonomers.
The preferred polyethylene-polysiloxane block copolymers of this invention and the general method of making them with hydrocabon solvents are fully described in U.S. Pat. No. 5,618,903, which is herein incorporated by reference. The improvement provided by the present invention is the use of a non-volatile oil or a polymer melt phase having a melting point in the polymerization temperature range for the cyclic siloxane and the comonomers; i.e., a low molecular polyethylene wax in the melt phase as the polymerization medium. This lowers the cost of and simplifies the polymerization process in that there is no need for costly hydrocarbon solvent removal and recycle. The preferred polyethylene wax should have a melting point in the range of 30 to 80° C. since this is the lower end of the range at which polymerization of these polymers is generally carried out.
Ethylene may be polymerized as described above with the addition that it is usually best to include a promoter, such as a diamine, to facilitate the reaction. Examples of these amines which include but are not limited to follow: N,N,N′,N′-tetramethylmethylenediamine (TMMDA), N,N,N′,N′-tetramethylethylenediamine (TMEDA), N,N,N′,N′-tetraethylethylenediamine (TEEDA), N,N,N′,N′tetramethyl-1,3-propanediamine (TMPDA), N,N,N′,N′-tetramethyl-1,4-butane-diamine (TMBDA), dipiperidinomethane (DIPIM), 1,2-dipiperidinoethane (DIPIE), 1,8-bis(dimethylamino)naph-thalene, N,N,N′,N′tetramethyl-o-phenylenediamine (TMOPDA), 1,2-dipyrolidinoethane (DIPIP), 1,3-dipiperidinopropane (DIPIP), 1,2-bis(2.6-dimethyl-piperidino)cyclohexane (BDMPC), sparteine, and the like.
The ethylene polymerization reaction can be carried out at 30° C. to 80° C., preferably 40° C. to 60° C. The ethylene pressure can be from 10 psig to 1000 psig, preferably 100 to 500 psig, The polymerization time can run from 10 minutes to 2 hours, preferably 30 minutes to 1 hour.
When the polymerization of the ethylene is complete, living polyethylene blocks are present in the polymerization polymer melt phase. These are perfectly linear polyethylene-alkyllithiums. These living polyethylenes can then be reacted with cyclic siloxane monomers (R
1
R
2
SiO)
n
, where n=3-10, R
1
, and R
2
=alkyl (C
1
-C
20
), alkenyl (C
2
-C
20
), hydrogen, benzyl or phenyl (including alkyl substituted aromatics and polycyclics) and R
1
and R
2
can be the same or different. Specific siloxane monomers include (Me
2
SiO)
3
, (MeHSiO)
3
, (Me
2
SiO)
4
, (Me
2
SiO)
5
, (MeHSiO)
4
, (MeHSiO)
5
, (Ph
2
SiO)
3
(Ph
2
SiO)
4
, (Ph
2
SiO)
5
, (PhHSiO)
4
, (PhHSiO)
5
, (PhHSiO)
3
, (vinylmethylSiO)
4
, (vinylmethylSiO)
5
, (vinylHSiO)
3
, (vinylHSiO)
4
, (vinylHSiO)
5
, (vinylmethylSiO)
3
, (PhMeSiO)
3
, (PhMeSiO)
4
, (PhMeSiO)
5
. Mixtures of monomers can also be used. When a polydimethylsiloxane block initiated with RLi is desired, the monomer is preferably hexamethylcyclo-trisiloxane (D3) or octamethylcyclotetra-siloxane (D4). The preferred polymer block is polydimethylsiloxane because of favorable kinetics with Li initiator. Additional poly-siloxane blocks can be added to the polymer based on the monomers described above.
This polymerization is carried out in the presence of a polar promoter, including, but not limited to, the promoter present during th
Haas Donald F.
Moore Margaret G.
Shell Oil Company
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